Induction of an interferon response by RNAi vectors in mammalian cells

DNA vectors that express short hairpin RNAs (shRNAs) from RNA polymerase III (Pol III) promoters are a promising new tool to reduce gene expression in mammalian cells. shRNAs are processed to small interfering RNAs (siRNAs) of 21 nucleotides (nt) that guide the cleavage of the cognate mRNA by the RNA-induced silencing complex. Although siRNAs are thought to be too short to induce interferon expression, we report here that a substantial number of shRNA vectors can trigger an interferon response.     

粉末材料压制过程的DEM分析

应用离散单元法(DEM)研究了粉末材料在开口容器中受到刚性凸模压制时的流动特点,获得了压制过程中颗粒的运动轨迹、运动速度以及粉末密度分布等重要信息;总结了几种典型的粉末流动模式,并在相关实验中得到了印证,说明了应用DEM分析具有强剪切行为的粉末流动是可行的,结论可供粉末冶金工艺和模具设计人员参考.     

Improvement on the inversion of kernel-driven BRDF model

Kernel-driven model was chosen to calculate global albedo in the project of multiangular remote sensor MODIS. The best kernels were selected by the venerable "least square" method. The result of this method was very unstable when only a small amount of angular observations is available. A new criterion has been estalished, called "least variance" for the kernel's selection. It takes into consideration the effects of model and measurement based on the information inverse theory. Several tests showed that "least variance" has many advantages. First, it is less sensitive to noises. Second, it operates well in small sample size. Third, it depends less on the sampling position.     

Thresholds and the resilience of Caribbean coral reefs

The deteriorating health of the world's coral reefs threatens global biodiversity, ecosystem function, and the livelihoods of millions of people living in tropical coastal regions. Reefs in the Caribbean are among the most heavily affected, having experienced mass disease-induced mortality of the herbivorous urchin Diadema antillarum in 1983 and two framework-building species of coral. Declining reef health is characterized by increases in macroalgae. A critical question is whether the observed macroalgal bloom on Caribbean reefs is easily reversible. To answer this question, we must resolve whether algal-dominated reefs are an alternative stable state of the ecosystem or simply the readily reversible result of a phase change along a gradient of some environmental or ecological parameter. Here, using a fully parameterized simulation model in combination with a simple analytical model, we show that Caribbean reefs became susceptible to alternative stable states once the urchin mortality event of 1983 confined the majority of grazing to parrotfishes. We reveal dramatic hysteresis in a natural system and define critical thresholds of grazing and coral cover beyond which resilience is lost. Most grazing thresholds lie near the upper level observed for parrotfishes in nature, suggesting that reefs are highly sensitive to parrotfish exploitation. Ecosystem thresholds can be combined with stochastic models of disturbance to identify targets for the restoration of ecosystem processes. We illustrate this principle by estimating the relationship between current reef state (coral cover and grazing) and the probability that the reef will withstand moderate hurricane intensity for two decades without becoming entrained in a shift towards a stable macroalgal-dominated state. Such targets may help reef managers face the challenge of addressing global disturbance at local scales.